Rapid exchange catheters having a sealed guidewire lumen and methods of making the same

ABSTRACT

Methods and devices for preventing fluid flow through the relatively short guidewire lumen of a rapid exchange catheter. The guidewire lumen for a rapid exchange catheter is provided with a narrowed or sealed section allowing for passage of a guidewire therethrough while preventing fluid flow while a guidewire is disposed therethrough. The narrowed or sealed section extends for a relatively short length of the guidewire lumen to avoid creating excessive friction between the guidewire and the guidewire lumen. In several embodiments the narrowed or sealed section is placed proximal of the distal end of the guidewire lumen.

FIELD OF THE INVENTION

The present invention is related to the field of medical devices. Moreparticularly, the present invention is related to rapid exchangecatheter technologies.

BACKGROUND OF THE INVENTION

Catheters are used in a variety of minimally invasive medicalprocedures. A major portion of the catheter field involves cathetersthat track over a guidewire, such as angioplasty catheters that are usedto advance an inflatable member over a guidewire to a desired vascularlocation. One advancement in this field has been the use of rapidexchange catheters in place of standard over-the-wire catheters.

A standard over-the-wire catheter typically tracks over a guidewire overits entire length such that, in order to maintain a distal guidewirelocation while exchanging the catheter, a guidewire extension or verylong guidewire is used. To exchange the standard over-the-wire catheter,the guidewire is held in place while the catheter is withdrawn. Theproximal end of the guidewire is held until the distal end of thecatheter exits the patient's body, while the distal end of the guidewireremains in the desired location, meaning that the guidewire, duringexchange, must be twice as long as the catheter.

A rapid exchange catheter tracks over the guidewire for only a shortdistal portion of the catheter. Examples of rapid exchange catheters,their use, and methods for making such catheters are illustrated byWilliams et al. in U.S. Pat. No. 6,409,863, the disclosure of which isincorporated herein by reference. The catheter shown by Williams et al.includes an outer member and a distally located inner member, with aballoon proximal end attached to the distal end of the outer member anda balloon distal end attached to the distal inner member. A proximalguidewire port is located distal of the proximal end of the catheter,with the distal inner member opening at its proximal end to the proximalguidewire port, and extending to the distal end of the catheter.

One difficulty which can arise with some rapid exchange catheters isthat an inner member defining the distal guidewire lumen may allowpassage of fluid therethrough. Because the proximal guidewire port istypically in view of fluoroscopic instruments, passage of contrast fluidused to visualize the treatment location (for example, the location of alesion in a blood vessel) proximally through the guidewire lumen can bemisinterpreted as indicating device failure during inflation of adistally located balloon. Reducing the diameter of the guidewire lumento prevent fluid passage, however, can make it more difficult to pushthe catheter over the guidewire. Reducing the slidability of thecatheter with respect to the guidewire (and vice-versa) can make it moredifficult to maintain and manipulate guidewire position, thereby makingthe physician's task of advancing a catheter over the guidewire moredifficult.

SUMMARY OF THE INVENTION

The present invention, in an illustrative embodiment, includes a rapidexchange catheter having an outer member and an inner member defining aguidewire lumen, with the outer member including a proximal guidewireport located distally of the proximal end of the catheter. The innermember extends from the proximal guidewire port to the distal end of thecatheter. The inner member includes a fluid stop portion (less than itstotal length) configured to prevent fluid flow therethrough when aguidewire is disposed through the inner member. In several embodiments,the fluid stop portion is disposed proximal the distal end of the innermember. In one such embodiment, a seal is disposed within the innermember. In another such embodiment, the inner member includes a neckedportion proximal its distal end.

The present invention, in additional illustrative embodiments, includesmethods of making a rapid exchange catheter having an inner memberadapted to receive a guidewire. The inner member is further adapted toprevent fluid flow therethrough when a guidewire is disposed through theinner member. In one such embodiment, a seal is placed in the innermember. In another embodiment, a portion of the inner member issubjected to pressure and heat while disposed over a mandrel having atapered or necked portion, such that a portion of the inner member necksdown to a narrowed diameter for a length less than the total length ofthe inner member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a portion of a rapid exchange type catheter in crosssection;

FIG. 2 shows, in partial cross section, an illustrative rapid exchangecatheter proximal guidewire port and proximal portion of a guidewirelumen having a fluid blocking means;

FIG. 3 shows, in partial cross section, an illustrative distal portionof a guidewire lumen for a rapid exchange catheter having a fluidblocking means;

FIG. 4 shows, in partial cross section, mandrels and tubular membersconfigured for a step in constructing a rapid exchange catheter withfluid blocking means in a proximal portion of the distal guidewirelumen;

FIG. 5 shows, in partial cross section, an illustrative rapid exchangeproximal guidewire port that may be constructed as shown in FIG. 4;

FIG. 6 shows, in partial cross section, mandrels and tubular membersconfigured for a step in constructing an alternative rapid exchangecatheter with fluid blocking means in the distal portion of the distalguidewire lumen;

FIG. 7 shows, in partial cross section, a distal end of an illustrativerapid exchange catheter that may be constructed as shown in FIG. 6;

FIG. 8 shows, in partial cross section, another distal end for anillustrative rapid exchange catheter; and,

FIGS. 9A-9B illustrate, in schematic section views, a rapid exchangeproximal guidewire port before and after a port molding method of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description should be read with reference to thedrawings. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

As used herein, the term “rapid exchange” should be understood asimparting the same or similar meanings as other terms used in thecatheter arts such as single operator exchange. In particular, “rapidexchange catheter” includes any catheter designed to enable exchange ofa catheter placed using a guidewire without requiring a guidewireextension or guidewire that is substantially longer than the catheteritself. While much of the following description and several of thefigures illustrate balloon catheters, other catheter types mayincorporate the improvements herein, including, for example, fluidinfusion cannulas, cutting instruments, non-balloon self-expanding stentdelivery catheters, and/or atherectomy devices. Vascular andnon-vascular (such as biliary or uretogenital) uses are contemplated.

FIG. 1 illustrates relevant features of a rapid exchange catheter 10.The catheter 10 includes a proximal end 12 and a distal end 14. An outertubular member 16 defines an inflation lumen, and an inner tubularmember 18 defines a guidewire lumen from a guidewire port 20 to thedistal end 14 of the catheter 10. The proximal end of a balloon 22 issecured to the distal end of the outer tubular member 16. The distal endof the balloon 22 is secured near the distal end of the inner tubularmember 18. While shown as a butt-joint, the balloon 22 is often bondedto the outer tubular member 16 by a process performed on an overlap ofthe two. The balloon 22 may be secured by any suitable manner, forexample, using heat or welding methods, or by the use of an adhesive.The outer tubular member 16 includes a proximal portion extending fromthe proximal end 12 to the guidewire port 20 and a distal portionextending from the guidewire port 20 to the balloon 22.

A number of designs for and additional features of a rapid exchangecatheter 10 have been developed. For example, the outer tubular member16 may be made up of several tubes connected to one another includinghypotubes, polymeric tubes, and/or reinforced polymeric tubes. Theballoon 22 may be inelastic or elastic. Rather than a side exit as shownin FIG. 1, the guidewire port 20 may face a generally axial direction.Core wires, transition support elements, and the like may also beprovided. A number of radiopaque markers may be provided at variouslocations, as desired. The inclusion or addition of any of thesefeatures should be understood as being optional features of thefollowing illustrative embodiments of the present invention.Furthermore, the exact location and manner of securement/attachmentbetween the various elements can vary widely as further optionalfeatures of the following illustrative embodiments. Finally, thematerials used are also a matter of design choice and may vary widelywithin the scope of the present invention.

FIG. 2 illustrates in cross section a guidewire port 36. The catheter 30is illustrated having an outer member 32 and an inner member 34. Duringuse, a difficulty which can arise is the backflow of contrast fluid fromthe distal end (not shown) of the catheter 30 through the inner member34 (which defines a guidewire lumen) to the guidewire port 36. Thecontrast fluid can then exit the catheter shaft and can appear, underfluoroscopy, to indicate catheter failure due to a leak at the guidewireport 36.

For example, a radiopaque fluid or saline including a radiopaquematerial may be used to inflate a balloon disposed on the distal end ofthe catheter 30. If radiopaque fluid was previously used to visualizethe area of treatment at the distal end of the catheter, it may (unlessprevented from doing so) flow up the inner member 34 to the guidewireport 36, and exit the catheter 30 there. If this occurs, it can appearas though the inflation fluid were leaking at the guidewire port 36.Observation of the fluid exiting at the guidewire port 36 canunnecessarily cause a practitioner to believe that the inflation lumenis leaking, halt the procedure, and remove and discard the catheter 30.This is costly in terms of practitioner and procedure time, materialsand products, and, most importantly, patient discomfort and stress.

To prevent such leakage or flow through the inner member 34, theillustrative catheter 30 is provided with a fluid stop structure 38,illustrated as a narrowing or bump in the lumen defined by the innermember 34. The fluid stop structure 38 may be a deposited material or aninserted piece of material such as a plastic, wax, leather, foam,rubber, artificial rubber, or any flexible material that can preventfluid flow through the inner member while a guidewire is disposedtherein. Preferably the fluid stop structure 38 is designed, coated, orotherwise constructed to avoid creating undue friction with a guidewire(not shown) passing therethrough. By including the fluid stop structure38, radiopaque fluid is prevented or substantially prevented fromexiting the catheter at the guidewire port 36.

FIG. 3 illustrates an alternative sealing structure. In FIG. 3, acatheter 40 with balloon 42 and inner member 44 includes a sealingstructure shown as seal 46 disposed near the distal end of the guidewirelumen. The seal 46 may be, for example, a seal material or seal itselfsecured inside of the inner member 44. Alternatively, the inner member44 may be provided as including an internal lumen irregularity thatfunctions as a seal 46 to prevent fluid flow through the inner member 44when a guidewire (not shown) is disposed therein. By moving the seal 46away from the distal tip of the catheter 40, it becomes easier tobackload a catheter over a guidewire (loading by inserting the proximalend of the guidewire into the distal end of the catheter 40 andadvancing the catheter 40 over the guidewire).

FIG. 4 illustrates a step in a process of making a rapid exchange typecatheter having a fluid blocking feature in its distal inner member. Inparticular, the catheter 50 is shown having integral parts including aproximal member 52, a distal outer member 54, and a distal inner member56. The proximal end 58 of the distal inner member 56 is shown asfitting onto a reduced size portion of a distal mandrel 64. A proximalmandrel 62 passes through the proximal member 52 past a guidewire port60.

Several designs may be used for the proximal end 58 of the distal innermember 56. The proximal end 58 of the distal inner member 56 may beformed as a tapered portion. Alternatively, the distal inner member 56may be a simple tubular member, with a triangular portion cut from itsproximal end 58 to allow the distal inner member 56 to be compressedaround the distal mandrel 64. In a preferred embodiment, the distalinner member 56 is a tubular member that is shaped over the distalmandrel 64 during a heat-welding step in which the proximal member 52 isattached to the distal outer member 54 and distal inner member 56 toform the port joint or guidewire port 60. To achieve such a structure,the proximal mandrel 62 may include a distal end having a crescent orhalf-moon transverse cross-sectional shape such that it can partiallysurround the distal inner member 56. In at least one embodiment, theproximal end 58 of the distal inner member 56 is sized to allowrelatively easy passage of a guidewire therethrough, while preventingundesired fluid flow.

One advantage of the embodiment of FIG. 4 is that it can be even easierto introduce a guidewire to the distal end (not shown) of the catheterthan with the embodiment in FIG. 3. This is due to the fact that thenarrowed portion of the inner members (44, 56) is the location at whichthe greatest friction will likely occur when a guidewire is advanced orwithdrawn. By placing the fluid restricting feature away from the distalend of the catheter, it becomes possible to advance the guidewirethrough a portion of the inner member before reaching thisfriction-creating point. Further, the opening at the distal end becomesbigger, and the inner/outer members may provide column strength foreasing passage of the guidewire without buckling either the catheter orthe guidewire.

For example, in several rapid exchange embodiments, the method ofintroduction over a guidewire includes back-loading the distal end ofthe catheter over the proximal end of a guidewire. This method can bedifficult using, for example, a structure as shown by Fitzmaurice et al.in U.S. Pat. No. 6,190,358, which shows necking of the guidewire memberat its distal tip. The distal tip will typically be quite soft andflexible, sometimes taking the form of a “bumper” tip to avoid damagingblood vessels during advancement. Typically the proximal end of aguidewire has the greatest diameter and stiffness for the guidewire.Getting the proximal tip of the guidewire into such a delicate and softstructure without damaging the catheter can be a challenge, particularlygiven that the practitioner will usually be wearing gloves. Furthermore,placing the necked portion right at the distal tip may stiffen the“bumper” tip, reducing its effectiveness in preventing damage tosurrounding tissue.

FIG. 5 illustrates, in section, the catheter 50 from FIG. 4 after awelding/fusing or other attachment step. It can be seen that thecatheter includes a proximal member 52, distal outer member 54, anddistal inner member 56. A guidewire port 60 is located at a port joint.Near the guidewire port 60 is a fluid restriction feature 66 shown as anarrowing of the guidewire lumen 70 defined by the distal inner member56. Note that it is not necessary for the distal inner member 56 toremain in contact with the distal outer member 54 distal of theguidewire port 60, where the catheter may assume a generallycoaxial/concentric configuration. The inflation lumen 68 may have acrescent shape across the port joint near the guidewire port 60, and maytake an annular shape distal of the guidewire port 60, as desired. Theintegral parts 52, 54, 56 are shown separately for illustrativepurposes. However, near the guidewire port 60 these parts will typicallyfuse and blend together to a certain extent.

FIG. 6 illustrates, in section, a method for providing a fluid blockingfeature near the distal end of a rapid exchange catheter. The catheter100 is illustrated having a balloon 102 attached at its distal end to aninner tubular member 104 and a distal bumper tip 106. The use of a verysoft or atraumatic bumper tip 106 makes advancement of a catheter in ablood vessel easier by improving trackability and avoiding vesseltrauma. Such softened tips may be used in other environments as well.The balloon 102 is secured by a heating process (such as a laser weldingprocess) over the butt-joint between the inner tubular member 104 andthe bumper tip 106. For the illustrative embodiment of FIG. 6, beforethe heating step to secure the balloon 102 to the inner tubular member104 and the bumper tip 106, mandrels 108, 110 are passed into the bumpertip 106 and inner tubular member 104, respectively. The mandrels 108,110 help maintain the shape and patency of the lumens for the innertubular member and bumper tip. To provide a fluid blocking feature, thetips of one or both of the mandrels may be notched, tapered or trimmedto provide a narrowed mandrel section.

After the various elements shown in FIG. 6 are subjected to a heatbonding step, the mandrels 108, 110 are removed and the configurationshown in FIG. 7 is the result. In particular, the balloon 102 is securedover the inner tubular member 104 and the bumper tip 106. A fluidblocking feature 112 has been created by plastic deformation during theheating step, with one or both of the inner tubular member 104 andbumper tip 106 being deformed around the mandrels 108, 110 to create anarrowed lumen section or lip. The fluid blocking feature 112 ispreferably sized to block fluid flow through the combination of theinner tubular member 104 and bumper tip 106 when a guidewire is disposedtherethrough. Because the fluid blocking feature 112 is not at thedistal tip of the bumper tip 106, instead being disposed proximallythereof, it may be easier to backload a guidewire (not shown) with thecatheter 100.

Typically the sizing of such catheters renders the distance from thedistal end for the fluid blocking feature 112 relatively long eventhough appearing, in terms of absolute magnitude, rather short. As anexample, the bumper tip 106 in some embodiments may have a length in therange of about 2-4 mm. A fluid blocking feature as shown in FIGS. 6-7would, therefore, be in the range of 2-4 mm from the distal end of thecatheter. As such, the distal opening of the inner member may be largeenough to facilitate backloading of a guidewire therein, with thechanging diameter of the guidewire lumen guiding the guidewire past thefluid blocking structure.

FIG. 8 shows, in partial cross section, another distal end for anillustrative rapid exchange catheter. The catheter 120 includes aballoon 122, an inner member 124, and a bumper tip 126. In theillustrative embodiment, the balloon 122 and bumper tip 126 form abutt-joint over the inner member 124. These three elements may besecured to one another by placing mandrels therethrough and subjectingthe joint(s) to heat. By using mandrels having a stepped or taperedportion, a fluid blocking structure 128 may be formed at the distal endof the inner member 124. In the illustration, the fluid blockingstructure 128 is formed using material from the distal end of the innermember 124. Such a formation may optionally be further facilitated bythe use of materials for the three elements shown 122, 124, 126 suchthat the inner member 124 flows more readily at a given temperature thanthe balloon 122 or bumper tip 124.

A number of molded port joints and subassemblies are illustrated incopending application Ser. No. 10/653,375, filed Sep. 2, 2003 andentitled CATHETER INCLUDING A UNIBODY DISTAL GUIDEWIRE PORT AND METHODOF MANUFACTURE, the disclosure of which is incorporated herein byreference. Modification of the mandrels illustrated therein may beperformed in accordance with the present invention to provide fluid flowstops in the guidewire lumens of embodiments therein.

For example, FIGS. 9A-9B illustrate, in schematic section views,mandrels and tubular members disposed prior to performing a molding stepto construct an insert molded port joint, and the port joint once socreated. As illustrated in FIG. 9A, a port mold 200 is provided defininga molding volume 202. A proximal member 204 is partly inserted to theport mold with a mandrel 206 extending distally therefrom. The mandrel206 extends through the molding volume 202 into a space between thedistal outer member 208 and distal inner member 210. The mandrel 206 mayinclude a proximal round section and a distal section having a taper orthat is crescent shaped to fit in the space between the distal innermember 210 and distal outer member 208.

A first guidewire mandrel 212 is provided extending from the port mold200 into the distal inner member 210. As can be seen, the end of thefirst guidewire mandrel 212 includes a portion of reduced diameter. Asecond guidewire mandrel 214 extends through the distal inner member 210from its distal end near the proximal end of the distal inner member210. The second guidewire mandrel 214 may be shaped at its end topartially mate with the first guidewire mandrel 212, as shown. However,there is a region where the first guidewire mandrel 212 has a lesserdiameter than that of the distal inner member 210 without the secondguidewire mandrel 214 extending thereto.

An injectate material is then forced into the port mold 200. Theinjectate material will be typically hot, and will provide pressure aswell. The combination of heat and pressure then causes the members 204,208, 210 to be secured together. As shown in FIG. 9B, when theinjection/heating/pressure step is completed, the members 204, 208, 210are secured to one another either directly or via the injected material216, which surrounds and adheres to each member 204, 208, 210. Aguidewire port 218 is provided by the use of the mandrels 212, 214 (notshown). A guidewire passage includes the interior of the guidewire port218 as well as the interior of the distal inner member 210. It can beseen that a fluid blocking feature 220 resides therein, as a result ofthe effects of heat and pressure on the area of the distal inner member210 near where the smaller diameter distal end of the first guidewiremandrel 212 was. Meanwhile, an inflation lumen 222 has been maintainedgoing through the port joint itself from the inner member 204 to thelumen between the distal inner member 210 and the distal outer member208.

Those skilled in the art will recognize that the present invention maybe manifested in a variety of forms other than the specific embodimentsdescribed and contemplated herein. Accordingly, departures in form anddetail may be made without departing from the scope and spirit of thepresent invention as described in the appended claims.

1. A rapid exchange catheter having a proximal end and a distal end, thecatheter comprising: an outer member having a proximal end and a distalend; and an inner member having a proximal end and a distal end;wherein: a guidewire port opens into the proximal end of the innermember at a location along the outer member distal of the proximal endof the outer member; the inner member extends distally inside the outermember from the guidewire port beyond the distal end of the outermember; the inner member is sized and adapted to receive a guidewiretherethrough, the inner member having a first diameter along a majorityof its length sufficient to allow fluid passage therethrough while theguidewire is disposed therethrough; and a seal is disposed within theinner member at a location spaced from the distal end of the innermember.
 2. The rapid exchange catheter of claim 1, wherein the seal islocated nearer the proximal end of the inner member than the distal endof the inner member.
 3. The rapid exchange catheter of claim 1, whereinthe inner member defines a first lumen and the outer member defines asecond lumen, the second lumen including a portion disposed between theinner member and the outer member, wherein the inner member preventsfluid flow from the second lumen into the first lumen.
 4. The rapidexchange catheter of claim 1, wherein the seal is formed at least inpart of material of the inner member.
 5. The rapid exchange catheter ofclaim 1 wherein the seal is formed at least in part of materialdeposited within the inner member.
 6. A rapid exchange catheter having aproximal end and a distal end, the catheter comprising: an outer memberhaving a proximal end and a distal end; and an inner member having aproximal end and a distal end; wherein: a guidewire port opens into theproximal end of the inner member at a location along the outer memberdistal of the proximal end of the outer member; the inner member extendsdistally from the guidewire port past the distal end of the outermember; the inner member is sized and adapted to receive a guidewiretherethrough without allowing passage of a fluid therethrough while theguidewire is disposed therethrough, the inner member having a firstdiameter along a majority of its length sufficient to allow fluidpassage therethrough while the guidewire is disposed therethrough; andthe inner member includes a tubular member having a necked portionspaced from the distal end of the inner member.
 7. The rapid exchangecatheter of claim 6, wherein the inner member includes a proximaltubular member and a bumper tip, the bumper tip and proximal tubularmember joining at a butt-joint, and the necked portion is formed at thebutt-joint using material from at least one of the bumper tip and theproximal tubular member.
 8. The rapid exchange catheter of claim 7,further comprising a balloon having a proximal balloon waist, a distalballoon waist, and a central balloon portion, wherein the distal balloonwaist overlaps the butt-joint between the bumper tip and the proximaltubular member.
 9. The rapid exchange catheter of claim 6, wherein theinner member includes a proximal tubular member and a bumper tip, thebumper tip forming a lap joint over the proximal tubular member, whereinthe necked portion is formed at the distal end of the proximal tubularmember beneath the bumper tip.
 10. The rapid exchange catheter of claim9, further comprising a balloon having a proximal balloon waist, adistal balloon waist, and a central balloon portion, wherein the distalballoon waist and the bumper tip form a butt-joint over the proximaltubular member.
 11. The rapid exchange catheter of claim 6, wherein thenecked portion is located nearer the proximal end of the inner memberthan the distal end of the inner member.
 12. The rapid exchange catheterof claim 11, further comprising a balloon having a proximal waist and adistal waist, the proximal waist being secured to the outer member andthe distal waist being secured to the inner member; wherein the outermember defines an inflation lumen and the inner member defines aguidewire lumen, the inflation lumen being in fluid communication withthe interior of the balloon, the inflation lumen being fluidly isolatedfrom the guidewire lumen by the inner member.
 13. The rapid exchangecatheter of claim 6, wherein the inner member defines a first lumen andthe outer member defines a second lumen, the second lumen including aportion disposed between the inner member and the outer member, whereinthe inner member prevents fluid flow from the second lumen into thefirst lumen.
 14. A method of fabricating a rapid exchange catheterhaving a proximal portion and a distal portion with a proximal guidewireport therebetween, the distal portion including a guidewire memberdefining the majority of a guidewire lumen having a proximal end at theproximal guidewire port and a distal end at the distal end of thecatheter, the method comprising providing a fluid flow stop means forpreventing fluid flow through the guidewire lumen at a location proximalof the distal end of the guidewire lumen.
 15. The method of claim 14,wherein the step of providing a fluid flow stop means includes insertinga seal member therein.
 16. The method of claim 14, wherein the step ofproviding a fluid flow stop means includes creating a necked portion ofthe guidewire lumen by applying heat to the guidewire member.
 17. Themethod of claim 16, wherein the rapid exchange catheter includes anouter member and the guidewire member, the guidewire member extendingdistally from the proximal guidewire port inside the outer member, therapid exchange catheter also including a balloon having a proximal waistsecured to the outer member and a distal waist secured to the guidewiremember, wherein the step of creating a necked portion of the guidewirelumen is performed as part of a process for securing the distal balloonwaist to the guidewire member.
 18. The method of claim 17, wherein theguidewire member of the rapid exchange catheter includes a proximaltubular member and a bumper tip, and wherein the step of creating anecked portion comprises: placing an end of the bumper tip adjacent adistal end of the distal balloon waist over the proximal tubular member;placing a mandrel inside the proximal tubular member and/or bumper tip,the mandrel having a stepped portion having a lesser diameter than otherportions of the mandrel, such that the stepped portion is adjacent adistal end of the proximal tubular member; and applying heat to securethe bumper tip, balloon, and proximal tubular member together; whereinthe necked portion is formed at a location corresponding to the distalend of the proximal tubular member.
 19. The method of claim 17, whereinthe inner member of the rapid exchange catheter includes a proximaltubular member and a bumper tip, and wherein the step of creating anecked portion comprises: placing a proximal end of the bumper tipadjacent a distal end of the proximal tubular member to form abutt-joint beneath the distal balloon waist; placing a mandrel insidethe proximal tubular member and/or bumper tip, the mandrel having astepped portion having a lesser diameter than other portions of themandrel, such that the stepped portion is adjacent the butt-joint; andapplying heat to secure the bumper tip, balloon, and proximal tubularmember together; wherein the necked portion is formed at a locationcorresponding to the butt-joint.
 20. The method of claim 14, wherein thestep of providing a fluid flow stop means includes providing a mandrelhaving a first diameter at a first location and a second diameter at asecond location, the second diameter being less than the first diameter,and the necked portion is formed by: inserting the mandrel into theguidewire lumen; and applying heat to the guidewire member at a locationcorresponding to the second location on the mandrel to reduce the innerdiameter of the guidewire member.
 21. The method of claim 14, whereinthe guidewire lumen extends distally from the proximal guidewire port,the proximal guidewire port being constructed in a molding step, whereinthe fluid flow stop means is formed during the molding step.
 22. Themethod of claim 14, wherein the fluid flow stop means is provided closerthe proximal end of the guidewire lumen than the distal end of theguidewire lumen.
 23. The method of claim 22, wherein the relativelyshort portion is constructed relatively near the guidewire port.
 24. Amethod of using a rapid exchange catheter comprising: providing a rapidexchange catheter having a proximal end, a distal end, a proximalsection, a proximal guidewire port, and a distal section, the distalsection defining a greater number of lumens than the proximal section,the distal section including a guidewire member having a proximal endopening into the guidewire port and a distal end extending to the distalend of the catheter, the guidewire member having a fluid stoppingstructure therein adapted to prevent fluid flow through the guidewiremember when a guidewire is disposed through the fluid stoppingstructure, the fluid stopping structure being disposed proximal of thedistal end of the guidewire member; inserting a proximal end of aguidewire to the distal end of the guidewire member; manipulating theguidewire and/or rapid exchange catheter to cause relative movementbetween the two to advance the guidewire proximally through theguidewire member up to the fluid stopping structure; and manipulatingthe guidewire and/or rapid exchange catheter to cause relative movementbetween the two to cause the guidewire to pass proximally of the fluidstopping structure.
 25. The method of claim 24, wherein the fluidstopping structure is provided nearer the proximal end of the guidewiremember than the distal end of the guidewire member.